中文摘要：

采用搅拌摩擦焊方法成功获得3种不同组合形式（搭接/对搭接/对接）的6061-T4铝合金T型接头。对接头的焊接缺陷、微观组织、硬度分布及抗拉强度分别进行观察和测试。结果表明：在前进侧圆角过渡区或筋板焊核区，3种接头均容易出现隧道缺陷；弱结合缺陷由于塑性变形偏离原始连接界面而向筋板或者壁板前进侧偏移；与常规搅拌摩擦焊对接搭接接头不同，T型接头沿筋板方向出现热机影响区和两个圆角过渡区；软化区域和弱结合是导致沿壁板拉伸强度降低的主要原因，而弱结合和隧道缺陷是引起这3种T型接头沿筋板方向断裂的重要原因。

英文摘要：

Three combination modes （T-lap/T-butt-lap/T-butt） of AA6061-T4 aluminum alloy T-joints were successfully jointed by friction stir welding. Welding defects, microstructure, hardness profiles and tensile strength of the obtained T-joints were observed and measured, respectively. The results show that tunnel defects are easily formed in the fillet zone of the advancing side or in stringer nugget zone for all the three modes of T-joints. Defects of kissing bond are extruded downward to the stringer or sideward from the original joining surfaces to the advancing side of the skin under severe plastic deformation. T-joints exhibit the thermo-mechanical affected zone and two fillet zones in the stringer, which are different from the conventional butt and lap joints of friction stir welding. Softening zones and kissing bond are the main reasons to reduce the tensile strength of T-joints along skin direction, and kissing bond and tunnel defects are the main reasons for the fractures of T-joints along stringer direction.